Web crippling of cold-formed steel built-up box sections

This research focused on the experiments, numerical simulations and design of cold-formed steel (CFS) built-up box sections failed by web crippling. The built-up box sections were formed by fastening two equal-sized unlipped channel sections face-to-face by self-tapping screws. Thirty-five web crippling tests are firstly described, which were conducted under Interior-Two-Flange (ITF), End-Two-Flange (ETF), Interior-One-Flange (IOF) and End-One-Flange (EOF) loading cases. The number and location of screws were varied along the channel flange width to study the influences of screw arrangements. The specimens were loaded along the major axis and the minor axis. Numerical simulations were also conducted. The experimental results were used in the development and validation of nonlinear finite element (FE) models. After validation, the validated numerical models were used for a comprehensive parametric investigation accounting for various cross-section dimensions, bearing lengths and screw arrangements. The experimental and numerical data were used to evaluate the design methods provided in the current design codes. Finally, two different design methods were proposed and assessed through the reliability analysis.